4340 steel and 4130 steel are both popular alloy steel grades with some distinct differences despite their similarities. Our team of steel experts broke down the key takeaways from a comparison of the two steel grades to help you understand which may be best for your project and its needs.
4130 Alloy Steel Overview
4130 steel is a low-alloy steel that contains high amounts of chromium and is often referred to as chromoly. 4130 steel has good machinability, ductility, weldability, and strength characteristics. It is used for many different industries, including automotive, aerospace, and machining.
4340 Alloy Steel Overview
4340 steel is a nickel-chromium-molybdenum alloy steel that is renowned for its superior strength. Most choose this steel grade for projects that require incredibly tough materials that will undergo high amounts of physical stress. It is used in a variety of industries for different applications, including automotive, aerospace, and tooling.
4130 vs 4140 Alloy Steel: Chemical Properties
The table below breaks down each chemical property of both steel grades.
| Chemical Property | 4130 Alloy Steel | 4340 Alloy Steel |
| Carbon, C | 0.30% | 0.40% |
| Manganese, Mn | 0.40-0.60% | 0.60-0.80% |
| Chromium, Cr | 0.80-1.10% | 0.70-0.90% |
| Molybdenum, Mo | 0.15-0.25% | 0.20-0.30% |
| Silicon, Si | 0.15-0.35% | 0.15-0.30% |
| Phosphorus, P (max) | 0.035% | 0.035% |
| Sulfur, S (max) | 0.040% | 0.040% |
4130 vs 4140 Alloy Steel: Mechanical Properties
In general, the treatment that steel undergoes greatly impacts its mechanical properties. Because of this, we’ve compiled two tables to highlight the mechanical properties of 4130 and 4140 steel based on their treatment.
Hot Rolled 4130 & 4340 Steel
| Mechanical Property | Hot Rolled 4130 Steel | Hot Rolled 4340 Steel |
| Tensile Strength | 97,000 psi | 185,500 psi |
| Yield Strength | 63,000 psi | 125,000 psi |
| Elongation (2″) | 25.5% | 12.2% |
| Reduction in Area | 59.5% | 36.3% |
| Brinell Hardness | 197 | 363 |
Cold Drawn 4130 & 4340 Steel
| Mechanical Property | Cold Drawn 4130 Steel | Cold Drawn 4340 Steel |
| Tensile Strength | 110 ksi min | 100 ksi min |
| Yield Strength | 95 ksi min | 90 ksi min |
| Elongation (2″) | 15% min | 15% min |
| Rockwell B (Hardness) | 95 | 93 |
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